If the carving bit is touching in areas where you don't expect it to carve, you can raise up by using masking tape or taping a playing card or two on top of the acrylic where the CW measures the thickness. I've had the machine carve off a layer of paint if the stock wasn't completely flat--it doesn't raise the bit up any more than it thinks that it needs to when travel to a new section of the carve.
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George
Life is short....drink the good wine first!